1. Field of the Invention
This invention relates to an inertia locking-type waterproof connector in which male and female connectors remain fitted together even if a change in ambient temperature occurs.
2. Discussion of the Related Art
FIG. 7 shows a conventional inertia locking-type waterproof connector disclosed in Japanese Utility Model Unexamined Publication No. 63-150479.
This inertia locking-type waterproof connector 32 comprises a male connector 33 having an elastic lock arm 22' supported at both of its ends, a female connector 34 having an engagement frame portion 25 for engaging a retaining projection 23' of the lock arm 22', a waterproof packing 36 mounted on a bottom of a fitting chamber 35 of the female connector 34, and a packing holder 37 for retaining the packing 36.
A slanting abutment surface 26' of the retaining projection 23' is formed at an angle close to a vertical plane. The male and female connectors 33 and 34 are fitted together by the application of an inertia force pushing the slanting surface 26' against its mating engagement frame portion 25. The packing 36 has mountain-like seal lips 29 and 38 that are sequentially brought into intimate sliding contact with an outer wall surface 39 of the male connector 33 when the connectors are fitted together.
FIG. 8 shows the force required for fitting the connectors together. Dot-and-dash line T' represents the insertion force T' between male and female terminals (not shown) respectively located within the connectors 33 and 34. Dots-and-dash lines labeled P.sub.1 ', and P.sub.2 ' respectively represent sliding resistances P.sub.1 ' and P.sub.2 ' between the seal lips 29 and 38 and the male connector 33. The sliding resistance P.sub.2 ' of the seal lip 38 is larger than that of seal lip 29 because it is cumulative with the sliding resistance of the seal lip 29. The solid line has peaks labeled R' and S' that respectively represent an abutting force R' between the lock arm 22' and the engagement frame portion 25 and a combined force S' representing the sum of the insertion force T' between the terminals and the sliding resistance P.sub.2 ' between the male connector 33 and the packing 36. As shown, the abutting force R' of the lock arm 22' is larger than the combined force S' of the terminals and the packing 36. Thus, when the abutment between the retaining projection 23' and the engagement frame portion 25 is released, the mating terminals are inserted and the intimate sliding resistance between the packing 36 and the male connector 33 has been overcome.
In this conventional construction, however, problems occur when the lock arm 22', which is typically comprised of a synthetic resin, hardens or softens due to changes in ambient temperature. In accordance with this change, the abutting force, or inertia locking force, R' between the retaining projection 23' and the engagement frame portion 25 increases or decreases. If the inertia locking force increases, as shown by the dashed line with peak R.sub.1 ' in FIG. 8, the efficiency of the fitting operation is adversely affected as a very high force is required to disengage the connectors. If the inertia locking force is smaller than the combined force S' of the terminals and the packing 36, as shown by the dashed line with peak R.sub.2 ', then a tight fit between the connectors is not achieved.